- #1
Physical_Fire
- 54
- 11
What's the difference between these two curves for AC Generator?
- Context: High School
- Thread starter Physical_Fire
- Start date
Click For Summary
Discussion Overview
The discussion revolves around the differences between two curves representing the output of an AC generator, focusing on their labeling, representation of current and voltage, and the implications of these differences in terms of electromagnetic induction and Faraday's law. Participants express confusion regarding the relationship between the curves and their respective cycles and revolutions.
Discussion Character
- Debate/contested
- Conceptual clarification
- Technical explanation
Main Points Raised
- Some participants note that one curve uses numbers for labels while the other uses letters, indicating a potential source of confusion.
- It is mentioned that one curve represents current and the other represents voltage, although this is presented with a light-hearted tone.
- One participant expresses confusion about the differences between the curves, questioning how to represent two revolutions and noting that the second picture resembles a cosine curve starting from 1.
- Another participant points out that the top picture in one post corresponds to the bottom picture in another, suggesting that confusion may arise from this mismatch.
- Faraday's law is referenced as an important relationship in understanding the curves, with a participant asking if others can see how the pictures agree with this law.
- Some participants request clarification on the concepts of electromagnetic induction and Faraday's law, indicating varying levels of understanding among the group.
- One participant argues that the figures can only be correctly interpreted together if the circuit contains only a resistor, as the presence of capacitors or coils would introduce a phase shift between EMF and current.
- Another participant asserts that there are no significant differences between the two curves other than stylistic choices, prompting a request for specificity in identifying perceived differences.
- A detailed explanation is provided, stating that the definitions of "1 cycle" and "one revolution" differ in terms of their starting points, which affects how the curves are interpreted in relation to time and rotations.
Areas of Agreement / Disagreement
Participants express differing views on the significance of the differences between the curves, with some asserting that they represent the same process while others highlight the importance of their distinct definitions and implications. The discussion remains unresolved regarding the clarity and interpretation of the curves.
Contextual Notes
There are limitations in the discussion regarding assumptions about the circuit components and the definitions of cycles and revolutions, which may affect the interpretation of the curves. The discussion also reflects varying levels of familiarity with the underlying principles of electromagnetic induction.
- #2
Dale
Mentor
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One uses numbers for labels while the other uses letters.
- #3
BvU
Science Advisor
Homework Helper
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And one is current, the other voltage 
You'll keep getting this kind of corny answers until you improve your question...
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You'll keep getting this kind of corny answers until you improve your question...
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- #4
Physical_Fire
- 54
- 11
Why are the curves different? One revolution in the yellow picture is different to the one underneath it. The second picture looks like a cosine curve if started from 1. And how would I know how to draw 2 revolution curve? I am confused.
- #5
BvU
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You're not doing it deliberately, but the top picture in post #1 goes with the bottom picture in #4. Confusion lurks 
.
An important relationship in this is Faraday's law: ##\quad\varepsilon = -{d\Phi\over dt}##.
Can you see how the two pictures agree in that respect ?
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.An important relationship in this is Faraday's law: ##\quad\varepsilon = -{d\Phi\over dt}##.
Can you see how the two pictures agree in that respect ?
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- #6
Physical_Fire
- 54
- 11
I don't get it. Please explain
- #7
BvU
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On what level ? What do you know already ? About electromagnetic induction, Faraday's law, AC generators, etc ?Physical_Fire said:
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- #8
Physical_Fire
- 54
- 11
Yeah I know those. I don't his equation although.
- #9
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The figures only can belong together if your circuit contains only a resistor, because if there were capacitors and/or coils present there'd be a phase shift between the EMF (sometimes confusingly called "voltage") and the current.
- #10
BvU
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I don't think we should complicate things for the OP .
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Ok, but the question wasPhysical_Fire said:
Lenz's law, Lorentz force, ... ?BvU said:
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- #11
Dale
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I don’t see any differences between the two pictures other than stylistic differences. The concept and the content are the same.Physical_Fire said:
Can you be very specific and clear about what you see that is different to you?
- #12
Gavran
- 324
- 201
There are two notes, “1 cycle” in the first picture and “one revolution” in the second picture. Each of them shows what one cycle is or what one revolution is. But the cycle showed by the note “1 cycle” in the first picture is not the same as the cycle showed by the note “one revolution” in the second picture. “1 cycle” defines a revolution that begins from no. of rotations = 0 or from Time = 0 s, while “one revolution” defines a revolution that begins from Time = T/4 or from no. of rotations = 1/4. Which one will be used depends on which picture will be used in the process description. Every curve pattern, which is a revolution, must satisfied the condition that it can start at Time = t, where t can be any real number and it must end at Time = t + T where T is a period.
There is not a difference between two curves in two different pictures. Both of them describe the same process. The first revolution, in accordance with the definition of a revolution by the note “1 cycle” in the first picture, in the first picture begins from no. of rotations = 0 where e.m.f. = 0 V. Corresponding value of no. of rotations = 0 in the first picture is Time = 0 s in the second picture. The first revolution, in accordance with the definition of a revolution by the note “1 cycle” in the first picture, in the second picture begins from Time = 0 s where E.m.f. = 0 V.
There is not a difference between two curves in two different pictures. Both of them describe the same process. The first revolution, in accordance with the definition of a revolution by the note “1 cycle” in the first picture, in the first picture begins from no. of rotations = 0 where e.m.f. = 0 V. Corresponding value of no. of rotations = 0 in the first picture is Time = 0 s in the second picture. The first revolution, in accordance with the definition of a revolution by the note “1 cycle” in the first picture, in the second picture begins from Time = 0 s where E.m.f. = 0 V.
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